Growing solid deuterium for UCN production

We have experimentally studied growing a large (about 1 liter) ortho-deuterium crystal in real UCN source cryostat and recorded the process optically using camera. The best quality was observed when directly from vapor phase. grown at different mass flows of deuterium annealed temperatures. Optimum conditions were found for both, obtaining an transparent cooling it down with minimal damage. that quality, final shape changes during annealing are very much dependent on temperature profile walls.